1. Field of the Invention
The present invention relates to a laminate sheet constituted by an adhesive sheet having a predetermined form which is laminated onto a release sheet, and more particularly to a laminate sheet which is capable of reducing defects that may be formed on the adhesive sheet when the laminate sheet is wound into a roll.
2. Description of the Related Art
A conventional laminate sheet in which adhesive labels are laminated onto a release sheet is shown in FIG. 20 (Publication of Examined Utility Model Application No. H6-18383 (FIG. 1), Publication of Patent Application No. H8-316175 (FIGS. 3 through 6)). In recent years, such laminate sheets have come to be used in the manufacture of optical discs in order to laminate a cover sheet onto the light-receiving surface of the optical disc. As shown in FIG. 20, a conventional laminate sheet 1P is constituted by a long release sheet 2P and cover sheet portions 301P (adhesive sheets) provided continuously in the longitudinal direction of the release sheet 2P. The cover sheet portion 301P is constituted by an adhesive layer 31P and a light-transmitting base material 32P and has an identical form to an optical disc.
The laminate sheet 1P is wound into a roll form, transported and stored in a rolled state, and used by being pulled from the roll. When the laminate sheet 1P is wound into a roll in this manner, the cover sheet portions 301P are wound over other cover sheet portions 301P, and at this time, as shown in FIG. 21, traces (arc-form traces) of the contours of the cover sheet portions 301P are formed on the other cover sheet portions 301P due to winding pressure.
In order to prevent such arc-form traces from forming on the cover sheet portions 301P, the laminate sheet 1P may be wound at a reduced winding pressure, but the problem with a roll which has been wound at a reduced winding pressure is that the roll is likely to collapse.
Further, when the laminate sheet 1P is wound, foreign matter such as minute dust particles (normally with a diameter of 5 to 50 μm) may become trapped between the wound layers of the laminate sheet 1P. If the laminate sheet 1P is wound with foreign matter trapped in this manner, depressions caused by the foreign matter are formed in the cover sheet portions 301P.
Such arc-form traces and depressions formed in the cover sheet portions 301P as described above do not cause great problems in conventional optical discs, but in next-generation high capacity/high recording density optical discs (Blu-ray Discs), these arc-form traces and depressions become defects which may cause errors when data are read.